An internal combustion engine such as a combustion engine of a motor vehicle generates a considerable quantity of heat during operation, which heat has to be conducted away from the internal combustion engine so that the operating temperature of the internal combustion engine does not increase above a maximum permissible temperature. If the maximum permissible temperature is exceeded, the engine power of the internal combustion engine must be lowered or the internal combustion engine must be stopped completely. In order to conduct away the heat from the internal combustion engine, the internal combustion engine is cooled with an engine coolant. The engine coolant, frequently water, is for this purpose pumped in a closed circuit through lines in the wall of the internal combustion engine where it absorbs some of the operational heat and in the process heats up. The heated engine coolant is subsequently conducted through a radiator where it outputs the absorbed heat into the surroundings. The radiator is usually arranged in a motor vehicle in such a way that there is a flow of relative wind through it, which flow is heated in the process and outputs the excess heat in this way to the surroundings.
In this context there is a problem that the cooling power of the radiator is variable. The cooling power of the radiator is determined not only by the difference between the respective variable temperatures of the engine coolant and of the ambient air but, in particular, by the velocity of the motor vehicle and therefore by the air mass flow rate through the radiator. The slower a motor vehicle travels, the less air flows through the radiator and therefore the lower the cooling power thereof. If, despite the low speed, the motor vehicle travels under high load, for example when traveling uphill with a heavy cargo as a result of a trailer, the radiator can no longer conduct away the operational heat which is produced, even with additional forced cooling by a radiator fan. This leads, as described above, to engine power having to be reduced or the internal combustion engine having to be stopped. As a result, the capability of the motor vehicle to move a heavy trailer load is thereby restricted.
The inventors herein have recognized issues with these approaches and herein disclose a method and device which permits a motor vehicle to move a larger trailer load. For example, when the method is implemented in an internal combustion engine of a vehicle, the method comprises determining a coolant temperature of an engine coolant of the internal combustion engine; comparing the coolant temperature with a predetermined threshold temperature; and reducing a thermal input into the engine coolant by changing at least one operating parameter of the internal combustion engine responsive to a coolant temperature higher than the predetermined threshold temperature. In one particular example described, a controller of a vehicle may be configured to increase a charging pressure of the internal combustion engine to reduce the thermal input into the engine coolant in response to a coolant temperature above the temperature threshold. The method further comprises determining a charge air temperature of a charge air of the internal combustion engine, and increasing the charge air pressure of the internal combustion engine based on the charge air temperature relative to a maximum charge air temperature. In this way, the technical result is achieved that a motor vehicle may operate under a heavy load, e.g., to move a heavy trailer load, without having to reduce an engine power.
The present disclosure has the further advantage that the thermal input from the internal combustion engine into the engine coolant is reduced by virtue of the fact that the internal combustion engine is operated according to changed operating parameters. However, as disclosed herein, the at least one operating parameter is changed in such a way that less heat is produced in the internal combustion engine while the engine power of the internal combustion engine is maintained at least virtually without modification. Therefore, although the instantaneous engine power may fall or rise as a result of the change in the at least one operating parameter, compensations may also be made, for example, by changing another operating parameter or by a control measure by the driver of the motor vehicle, that produces the result that the engine power remains approximately the same responsive to the change of the operating parameter.
In the example described, the thermal input into the engine coolant may be reduced by raising a charging pressure of the internal combustion engine. Increasing the charging pressure results in an increased mass flow through the internal combustion engine since the combustion air is compressed to a greater degree. In this way, a larger mass of air enters the internal combustion engine and correspondingly applies a greater cooling effect to the engine. That is, when the charging pressure is increased the temperature of the exhaust gas is also lowered, which may act to cool the engine.
In this context, a charge air temperature of a charge air of the internal combustion engine may be determined and the charging pressure of the internal combustion engine may be increased as a function of the charge air temperature. By determining the charge air temperature, it is possible to detect how far the charge air temperature is below a maximum desired charge air temperature (e.g., a maximum operating temperature threshold). By compressing the sucked-in air, the temperature of the air is increased. Therefore, the charge air temperature is also increased accordingly when the charging pressure of the internal combustion engine is increased. As such, in order to avoid increasing the charge air temperature to an undesirably large degree, it is advantageous to determine the charge air temperature and to increase the charging pressure as a function of the determined charge air temperature.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.